1. Field of the Invention
The present invention relates to a powder mixture to be made into an evaporation source material for use in ion plating, an evaporation source material for use in ion plating and a method of producing the same, and a gas barrier sheet and a method of producing the same. More particularly, the present invention relates to a powder mixture to be made into an evaporation source material for use in ion plating, capable of forming a gas barrier film that is dense and has good adhesive properties, and to others.
2. Background Art
A gas barrier sheet having, on a substrate, a film of an inorganic oxide such as silicon oxide or aluminum oxide, serving as a gas barrier film, has been proposed as a gas barrier sheet impermeable to oxygen gas, water vapor, etc. Since gas barrier sheets of this sort are excellent in transparency and have little influence on environments, demand for them is highly expected to grow in such areas as packaging materials.
Besides vacuum vapor deposition and sputtering, ion plating is employed as a process of depositing an inorganic oxide film that serves as a gas barrier film. In terms of adhesion to substrate and denseness, a gas barrier film formed by ion plating is superior to one deposited by vacuum vapor deposition and is comparable to one formed by sputtering. On the other hand, the rate of gas barrier film deposition in ion plating is higher than that in sputtering and is nearly equal to that in vacuum vapor deposition.
A gas barrier film formed by ion plating having the above-described features is described in Japanese Laid-Open Patent Publication No. 2000-272044 (Patent Document 1), for example. Patent Document 1 (claim 1) describes a transparent barrier film that is a thin film formed by ion plating using as a source SiOx (0≦x≦2), composed mainly of silicon oxide (SiOy (1.5≦y≦2)), having an oxygen permeability of 0.02-0.5 cc/m2·day.
Silicon oxide materials are inexpensive. They are therefore suitable for use as gas barrier films in such areas as packaging materials for foods and the like in which there is a demand for reduction in cost.
The gas barrier film described in Patent Document 1 has the required gas barrier properties. In recent years, however, demands for packaging materials of better performance have become stronger than ever, and the present goal in this area is making an overall improvement in gas barrier properties by suppressing not only oxygen permeability but also water vapor permeability. For example, also in such areas as foods in which packaging materials require a large reduction in cost, there is a growing demand for development of gas barrier sheets having more excellent gas barrier properties than ever, without an increase in cost.
The present invention was accomplished in order to fulfil the above-described goal in the art. An object of the present invention is therefore to provide a powder mixture to be made into an evaporation source material for use in ion plating, capable of forming a gas barrier film that is dense and is excellent in gas barrier properties, while keeping the cost low. More specifically, an object of the present invention is to provide a powder mixture to be made into an evaporation source material useful for ion plating, an evaporation source material for use in ion plating and a method of producing it, and a gas barrier sheet and a method of producing it.